In the formation of dams, such as movable wicket dams, across a body of moving water, such as a river or tidal inlet, costly and time consuming procedures are normally required. Normally, in such dam formations, large areas of the body of moving water are separated from the remainder by the construction of large cofferdams. After construction of a cofferdam, which is generally formed by sections of sheet metal piling which cooperate with each other to form a watertight enclosure, the interior of the cofferdam has the water pumped therefrom to expose the bed or floor of the body of water within the cofferdam, and construction of a permanent foundation and other superimposed structure is effected under dry conditions. By isolating a large dry area, dredging or removal of a portion of the bed may be effected within the enclosure and a solid concrete or masonry structure can be formed on the dredged area.
Such "dry" methods of construction involve the use of large field labor forces which may not be locally available. Such cofferdams are not only expensive to construct, but they must remain in place for a long period of time, which restricts water flow substantially over long periods of high river flow and requires a long overall construction period. Also, such a construction method often requires the closing off of substantial areas of a river, thereby progressively increasing the flow of water through an ever-decreasing gap in the river until the drop of river level across the dam area is so great that lockage of river traffic is required, even during low water conditions.
The use of prefabricated wicket dams and the placement of said wicket dams on immersed foundations have been proposed, as in U.S. Pat. Nos. 3,720,067; 3,775,983; 3,938,342 and 4,352,592, all of which issued to Jean Aubert. These patents describe a system of remotely fabricated wickets to be built and made operative on a remotely fabricated sill which is then brought to the site, submerged into a prepared sheetpile wall foundation, and secured into position with concrete, using underwater concreting techniques, and avoids extensive cofferdaming systems. While such a method is effective, it is primarily concerned with formation of a dam that comprises a single prefabricated sill and wicket system that is secured to a single foundation, and does not address the problems of multiple sill sections of a dam constructed across a wide expanse of a body of moving water with highly fluctuating water levels and velocities or large volumes of sediments or debris moving with the water.
It is an object of the present invention to incorporate a series of generally known and proven techniques into an overall system to provide the means to simplify and speed construction of large dams without the necessity of blocking off large areas of a body of moving water for extended periods of time, and a means to use effectively prefabricated units to provide the movable parts of the dam for ultimate water control, in a manner to provide for highly fluctuating water levels and velocities and/or silt loads.